diff --git a/packages/adapters/opencode-local/src/server/runtime-config.test.ts b/packages/adapters/opencode-local/src/server/runtime-config.test.ts
index 19f61c06d3..14791829a8 100644
--- a/packages/adapters/opencode-local/src/server/runtime-config.test.ts
+++ b/packages/adapters/opencode-local/src/server/runtime-config.test.ts
@@ -249,6 +249,67 @@ describe("prepareOpenCodeRuntimeConfig", () => {
     await prepared.cleanup();
   });
 
+  it("registers a configured model missing from the catalog on its provider", async () => {
+    const configHome = await makeConfigHome({ permission: { read: "allow" } });
+    const prepared = await prepareOpenCodeRuntimeConfig({
+      env: { XDG_CONFIG_HOME: configHome },
+      config: { model: "openrouter/openai/gpt-oss-120b:nitro" },
+    });
+    cleanupPaths.add(prepared.env.XDG_CONFIG_HOME);
+    const runtimeConfig = JSON.parse(
+      await fs.readFile(path.join(prepared.env.XDG_CONFIG_HOME, "opencode", "opencode.json"), "utf8"),
+    ) as { provider?: Record<string, { models?: Record<string, unknown> }> };
+    expect(runtimeConfig.provider?.openrouter?.models).toEqual({
+      "openai/gpt-oss-120b:nitro": {},
+    });
+    expect(prepared.notes).toContain(
+      "Registered configured model openrouter/openai/gpt-oss-120b:nitro in the runtime OpenCode config.",
+    );
+    await prepared.cleanup();
+  });
+
+  it("does not clobber an explicit model definition when registering the configured model", async () => {
+    const configHome = await makeConfigHome({ permission: { read: "allow" } });
+    const providers = {
+      openrouter: {
+        models: {
+          "openai/gpt-oss-120b:nitro": { name: "GPT-OSS 120B (nitro)" },
+          "example/other": {},
+        },
+      },
+    };
+    const prepared = await prepareOpenCodeRuntimeConfig({
+      env: {
+        XDG_CONFIG_HOME: configHome,
+        PAPERCLIP_OPENCODE_PROVIDERS: JSON.stringify(providers),
+      },
+      config: { model: "openrouter/openai/gpt-oss-120b:nitro" },
+    });
+    cleanupPaths.add(prepared.env.XDG_CONFIG_HOME);
+    const runtimeConfig = JSON.parse(
+      await fs.readFile(path.join(prepared.env.XDG_CONFIG_HOME, "opencode", "opencode.json"), "utf8"),
+    ) as { provider?: Record<string, { models?: Record<string, unknown> }> };
+    expect(runtimeConfig.provider?.openrouter?.models).toEqual(providers.openrouter.models);
+    expect(
+      prepared.notes.some((note) => note.startsWith("Registered configured model")),
+    ).toBe(false);
+    await prepared.cleanup();
+  });
+
+  it("skips model registration when the configured model is not provider/model shaped", async () => {
+    const configHome = await makeConfigHome({ permission: { read: "allow" } });
+    const prepared = await prepareOpenCodeRuntimeConfig({
+      env: { XDG_CONFIG_HOME: configHome },
+      config: { model: "not-a-provider-model" },
+    });
+    cleanupPaths.add(prepared.env.XDG_CONFIG_HOME);
+    const runtimeConfig = JSON.parse(
+      await fs.readFile(path.join(prepared.env.XDG_CONFIG_HOME, "opencode", "opencode.json"), "utf8"),
+    ) as Record<string, unknown>;
+    expect(runtimeConfig.provider).toBeUndefined();
+    await prepared.cleanup();
+  });
+
   it("respects explicit opt-out", async () => {
     const configHome = await makeConfigHome();
     const prepared = await prepareOpenCodeRuntimeConfig({
diff --git a/packages/adapters/opencode-local/src/server/runtime-config.ts b/packages/adapters/opencode-local/src/server/runtime-config.ts
index 146b371f29..dd466cdb2d 100644
--- a/packages/adapters/opencode-local/src/server/runtime-config.ts
+++ b/packages/adapters/opencode-local/src/server/runtime-config.ts
@@ -84,6 +84,14 @@ function parseProviderConfig(
   return Object.keys(providers).length > 0 ? providers : null;
 }
 
+function parseConfiguredModelRef(raw: unknown): { provider: string; model: string } | null {
+  if (typeof raw !== "string") return null;
+  const trimmed = raw.trim();
+  const slash = trimmed.indexOf("/");
+  if (slash <= 0 || slash === trimmed.length - 1) return null;
+  return { provider: trimmed.slice(0, slash), model: trimmed.slice(slash + 1) };
+}
+
 async function readJsonObject(filepath: string): Promise<Record<string, unknown>> {
   try {
     const raw = await fs.readFile(filepath, "utf8");
@@ -162,7 +170,7 @@ export async function prepareOpenCodeRuntimeConfig(input: {
     notes,
   );
   const existingProvider = isPlainObject(existingConfig.provider) ? existingConfig.provider : {};
-  const nextProvider = gatewayProviders
+  let nextProvider = gatewayProviders
     ? { ...existingProvider, ...gatewayProviders }
     : existingProvider;
   if (gatewayProviders) {
@@ -171,6 +179,32 @@ export async function prepareOpenCodeRuntimeConfig(input: {
     );
   }
 
+  // Register the configured model on its provider's models map. OpenCode resolves
+  // `--model provider/model` only when the model id exists in that map, so ids the
+  // models.dev catalog does not carry — OpenRouter routing variants such as
+  // `openai/gpt-oss-120b:nitro`, or models newer than the bundled catalog — are
+  // otherwise rejected with "Model not found" even though the provider serves them.
+  // An empty entry deep-merges with catalog metadata, so this is a no-op for models
+  // the catalog already knows, and we never clobber an explicit definition from the
+  // user config or PAPERCLIP_OPENCODE_PROVIDERS.
+  const configuredModel = parseConfiguredModelRef(input.config.model);
+  if (configuredModel) {
+    const providerEntry = isPlainObject(nextProvider[configuredModel.provider])
+      ? { ...(nextProvider[configuredModel.provider] as Record<string, unknown>) }
+      : {};
+    const providerModels = isPlainObject(providerEntry.models)
+      ? { ...(providerEntry.models as Record<string, unknown>) }
+      : {};
+    if (!isPlainObject(providerModels[configuredModel.model])) {
+      providerModels[configuredModel.model] = {};
+      providerEntry.models = providerModels;
+      nextProvider = { ...nextProvider, [configuredModel.provider]: providerEntry };
+      notes.push(
+        `Registered configured model ${configuredModel.provider}/${configuredModel.model} in the runtime OpenCode config.`,
+      );
+    }
+  }
+
   const nextConfig: Record<string, unknown> = {
     ...existingConfig,
     permission: {